/*
 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package java.io;

import java.nio.channels.FileChannel;
import sun.nio.ch.FileChannelImpl;


/**
 * Instances of this class support both reading and writing to a
 * random access file. A random access file behaves like a large
 * array of bytes stored in the file system. There is a kind of cursor,
 * or index into the implied array, called the <em>file pointer</em>;
 * input operations read bytes starting at the file pointer and advance
 * the file pointer past the bytes read. If the random access file is
 * created in read/write mode, then output operations are also available;
 * output operations write bytes starting at the file pointer and advance
 * the file pointer past the bytes written. Output operations that write
 * past the current end of the implied array cause the array to be
 * extended. The file pointer can be read by the
 * {@code getFilePointer} method and set by the {@code seek}
 * method.
 * <p>
 * It is generally true of all the reading routines in this class that
 * if end-of-file is reached before the desired number of bytes has been
 * read, an {@code EOFException} (which is a kind of
 * {@code IOException}) is thrown. If any byte cannot be read for
 * any reason other than end-of-file, an {@code IOException} other
 * than {@code EOFException} is thrown. In particular, an
 * {@code IOException} may be thrown if the stream has been closed.
 *
 * @author unascribed
 * @since JDK1.0
 */

public class RandomAccessFile implements DataOutput, DataInput, Closeable {

  private FileDescriptor fd;
  private FileChannel channel = null;
  private boolean rw;

  /**
   * The path of the referenced file
   * (null if the stream is created with a file descriptor)
   */
  private final String path;

  private Object closeLock = new Object();
  private volatile boolean closed = false;

  private static final int O_RDONLY = 1;
  private static final int O_RDWR = 2;
  private static final int O_SYNC = 4;
  private static final int O_DSYNC = 8;

  /**
   * Creates a random access file stream to read from, and optionally
   * to write to, a file with the specified name. A new
   * {@link FileDescriptor} object is created to represent the
   * connection to the file.
   *
   * <p> The <tt>mode</tt> argument specifies the access mode with which the
   * file is to be opened.  The permitted values and their meanings are as
   * specified for the <a
   * href="#mode"><tt>RandomAccessFile(File,String)</tt></a> constructor.
   *
   * <p>
   * If there is a security manager, its {@code checkRead} method
   * is called with the {@code name} argument
   * as its argument to see if read access to the file is allowed.
   * If the mode allows writing, the security manager's
   * {@code checkWrite} method
   * is also called with the {@code name} argument
   * as its argument to see if write access to the file is allowed.
   *
   * @param name the system-dependent filename
   * @param mode the access <a href="#mode">mode</a>
   * @throws IllegalArgumentException if the mode argument is not equal to one of <tt>"r"</tt>,
   * <tt>"rw"</tt>, <tt>"rws"</tt>, or <tt>"rwd"</tt>
   * @throws FileNotFoundException if the mode is <tt>"r"</tt> but the given string does not denote
   * an existing regular file, or if the mode begins with <tt>"rw"</tt> but the given string does
   * not denote an existing, writable regular file and a new regular file of that name cannot be
   * created, or if some other error occurs while opening or creating the file
   * @throws SecurityException if a security manager exists and its {@code checkRead} method denies
   * read access to the file or the mode is "rw" and the security manager's {@code checkWrite}
   * method denies write access to the file
   * @revised 1.4
   * @spec JSR-51
   * @see java.lang.SecurityException
   * @see java.lang.SecurityManager#checkRead(java.lang.String)
   * @see java.lang.SecurityManager#checkWrite(java.lang.String)
   */
  public RandomAccessFile(String name, String mode)
      throws FileNotFoundException {
    this(name != null ? new File(name) : null, mode);
  }

  /**
   * Creates a random access file stream to read from, and optionally to
   * write to, the file specified by the {@link File} argument.  A new {@link
   * FileDescriptor} object is created to represent this file connection.
   *
   * <p>The <a name="mode"><tt>mode</tt></a> argument specifies the access mode
   * in which the file is to be opened.  The permitted values and their
   * meanings are:
   *
   * <table summary="Access mode permitted values and meanings">
   * <tr><th align="left">Value</th><th align="left">Meaning</th></tr>
   * <tr><td valign="top"><tt>"r"</tt></td>
   * <td> Open for reading only.  Invoking any of the <tt>write</tt>
   * methods of the resulting object will cause an {@link
   * java.io.IOException} to be thrown. </td></tr>
   * <tr><td valign="top"><tt>"rw"</tt></td>
   * <td> Open for reading and writing.  If the file does not already
   * exist then an attempt will be made to create it. </td></tr>
   * <tr><td valign="top"><tt>"rws"</tt></td>
   * <td> Open for reading and writing, as with <tt>"rw"</tt>, and also
   * require that every update to the file's content or metadata be
   * written synchronously to the underlying storage device.  </td></tr>
   * <tr><td valign="top"><tt>"rwd"&nbsp;&nbsp;</tt></td>
   * <td> Open for reading and writing, as with <tt>"rw"</tt>, and also
   * require that every update to the file's content be written
   * synchronously to the underlying storage device. </td></tr>
   * </table>
   *
   * The <tt>"rws"</tt> and <tt>"rwd"</tt> modes work much like the {@link
   * java.nio.channels.FileChannel#force(boolean) force(boolean)} method of
   * the {@link java.nio.channels.FileChannel} class, passing arguments of
   * <tt>true</tt> and <tt>false</tt>, respectively, except that they always
   * apply to every I/O operation and are therefore often more efficient.  If
   * the file resides on a local storage device then when an invocation of a
   * method of this class returns it is guaranteed that all changes made to
   * the file by that invocation will have been written to that device.  This
   * is useful for ensuring that critical information is not lost in the
   * event of a system crash.  If the file does not reside on a local device
   * then no such guarantee is made.
   *
   * <p>The <tt>"rwd"</tt> mode can be used to reduce the number of I/O
   * operations performed.  Using <tt>"rwd"</tt> only requires updates to the
   * file's content to be written to storage; using <tt>"rws"</tt> requires
   * updates to both the file's content and its metadata to be written, which
   * generally requires at least one more low-level I/O operation.
   *
   * <p>If there is a security manager, its {@code checkRead} method is
   * called with the pathname of the {@code file} argument as its
   * argument to see if read access to the file is allowed.  If the mode
   * allows writing, the security manager's {@code checkWrite} method is
   * also called with the path argument to see if write access to the file is
   * allowed.
   *
   * @param file the file object
   * @param mode the access mode, as described <a href="#mode">above</a>
   * @throws IllegalArgumentException if the mode argument is not equal to one of <tt>"r"</tt>,
   * <tt>"rw"</tt>, <tt>"rws"</tt>, or <tt>"rwd"</tt>
   * @throws FileNotFoundException if the mode is <tt>"r"</tt> but the given file object does not
   * denote an existing regular file, or if the mode begins with <tt>"rw"</tt> but the given file
   * object does not denote an existing, writable regular file and a new regular file of that name
   * cannot be created, or if some other error occurs while opening or creating the file
   * @throws SecurityException if a security manager exists and its {@code checkRead} method denies
   * read access to the file or the mode is "rw" and the security manager's {@code checkWrite}
   * method denies write access to the file
   * @revised 1.4
   * @spec JSR-51
   * @see java.lang.SecurityManager#checkRead(java.lang.String)
   * @see java.lang.SecurityManager#checkWrite(java.lang.String)
   * @see java.nio.channels.FileChannel#force(boolean)
   */
  public RandomAccessFile(File file, String mode)
      throws FileNotFoundException {
    String name = (file != null ? file.getPath() : null);
    int imode = -1;
    if (mode.equals("r")) {
      imode = O_RDONLY;
    } else if (mode.startsWith("rw")) {
      imode = O_RDWR;
      rw = true;
      if (mode.length() > 2) {
        if (mode.equals("rws")) {
          imode |= O_SYNC;
        } else if (mode.equals("rwd")) {
          imode |= O_DSYNC;
        } else {
          imode = -1;
        }
      }
    }
    if (imode < 0) {
      throw new IllegalArgumentException("Illegal mode \"" + mode
          + "\" must be one of "
          + "\"r\", \"rw\", \"rws\","
          + " or \"rwd\"");
    }
    SecurityManager security = System.getSecurityManager();
    if (security != null) {
      security.checkRead(name);
      if (rw) {
        security.checkWrite(name);
      }
    }
    if (name == null) {
      throw new NullPointerException();
    }
    if (file.isInvalid()) {
      throw new FileNotFoundException("Invalid file path");
    }
    fd = new FileDescriptor();
    fd.attach(this);
    path = name;
    open(name, imode);
  }

  /**
   * Returns the opaque file descriptor object associated with this
   * stream.
   *
   * @return the file descriptor object associated with this stream.
   * @throws IOException if an I/O error occurs.
   * @see java.io.FileDescriptor
   */
  public final FileDescriptor getFD() throws IOException {
    if (fd != null) {
      return fd;
    }
    throw new IOException();
  }

  /**
   * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
   * object associated with this file.
   *
   * <p> The {@link java.nio.channels.FileChannel#position()
   * position} of the returned channel will always be equal to
   * this object's file-pointer offset as returned by the {@link
   * #getFilePointer getFilePointer} method.  Changing this object's
   * file-pointer offset, whether explicitly or by reading or writing bytes,
   * will change the position of the channel, and vice versa.  Changing the
   * file's length via this object will change the length seen via the file
   * channel, and vice versa.
   *
   * @return the file channel associated with this file
   * @spec JSR-51
   * @since 1.4
   */
  public final FileChannel getChannel() {
    synchronized (this) {
      if (channel == null) {
        channel = FileChannelImpl.open(fd, path, true, rw, this);
      }
      return channel;
    }
  }

  /**
   * Opens a file and returns the file descriptor.  The file is
   * opened in read-write mode if the O_RDWR bit in {@code mode}
   * is true, else the file is opened as read-only.
   * If the {@code name} refers to a directory, an IOException
   * is thrown.
   *
   * @param name the name of the file
   * @param mode the mode flags, a combination of the O_ constants defined above
   */
  private native void open0(String name, int mode)
      throws FileNotFoundException;

  // wrap native call to allow instrumentation

  /**
   * Opens a file and returns the file descriptor.  The file is
   * opened in read-write mode if the O_RDWR bit in {@code mode}
   * is true, else the file is opened as read-only.
   * If the {@code name} refers to a directory, an IOException
   * is thrown.
   *
   * @param name the name of the file
   * @param mode the mode flags, a combination of the O_ constants defined above
   */
  private void open(String name, int mode)
      throws FileNotFoundException {
    open0(name, mode);
  }

  // 'Read' primitives

  /**
   * Reads a byte of data from this file. The byte is returned as an
   * integer in the range 0 to 255 ({@code 0x00-0x0ff}). This
   * method blocks if no input is yet available.
   * <p>
   * Although {@code RandomAccessFile} is not a subclass of
   * {@code InputStream}, this method behaves in exactly the same
   * way as the {@link InputStream#read()} method of
   * {@code InputStream}.
   *
   * @return the next byte of data, or {@code -1} if the end of the file has been reached.
   * @throws IOException if an I/O error occurs. Not thrown if end-of-file has been reached.
   */
  public int read() throws IOException {
    return read0();
  }

  private native int read0() throws IOException;

  /**
   * Reads a sub array as a sequence of bytes.
   *
   * @param b the buffer into which the data is read.
   * @param off the start offset of the data.
   * @param len the number of bytes to read.
   * @throws IOException If an I/O error has occurred.
   */
  private native int readBytes(byte b[], int off, int len) throws IOException;

  /**
   * Reads up to {@code len} bytes of data from this file into an
   * array of bytes. This method blocks until at least one byte of input
   * is available.
   * <p>
   * Although {@code RandomAccessFile} is not a subclass of
   * {@code InputStream}, this method behaves in exactly the
   * same way as the {@link InputStream#read(byte[], int, int)} method of
   * {@code InputStream}.
   *
   * @param b the buffer into which the data is read.
   * @param off the start offset in array {@code b} at which the data is written.
   * @param len the maximum number of bytes read.
   * @return the total number of bytes read into the buffer, or {@code -1} if there is no more data
   * because the end of the file has been reached.
   * @throws IOException If the first byte cannot be read for any reason other than end of file, or
   * if the random access file has been closed, or if some other I/O error occurs.
   * @throws NullPointerException If {@code b} is {@code null}.
   * @throws IndexOutOfBoundsException If {@code off} is negative, {@code len} is negative, or
   * {@code len} is greater than {@code b.length - off}
   */
  public int read(byte b[], int off, int len) throws IOException {
    return readBytes(b, off, len);
  }

  /**
   * Reads up to {@code b.length} bytes of data from this file
   * into an array of bytes. This method blocks until at least one byte
   * of input is available.
   * <p>
   * Although {@code RandomAccessFile} is not a subclass of
   * {@code InputStream}, this method behaves in exactly the
   * same way as the {@link InputStream#read(byte[])} method of
   * {@code InputStream}.
   *
   * @param b the buffer into which the data is read.
   * @return the total number of bytes read into the buffer, or {@code -1} if there is no more data
   * because the end of this file has been reached.
   * @throws IOException If the first byte cannot be read for any reason other than end of file, or
   * if the random access file has been closed, or if some other I/O error occurs.
   * @throws NullPointerException If {@code b} is {@code null}.
   */
  public int read(byte b[]) throws IOException {
    return readBytes(b, 0, b.length);
  }

  /**
   * Reads {@code b.length} bytes from this file into the byte
   * array, starting at the current file pointer. This method reads
   * repeatedly from the file until the requested number of bytes are
   * read. This method blocks until the requested number of bytes are
   * read, the end of the stream is detected, or an exception is thrown.
   *
   * @param b the buffer into which the data is read.
   * @throws EOFException if this file reaches the end before reading all the bytes.
   * @throws IOException if an I/O error occurs.
   */
  public final void readFully(byte b[]) throws IOException {
    readFully(b, 0, b.length);
  }

  /**
   * Reads exactly {@code len} bytes from this file into the byte
   * array, starting at the current file pointer. This method reads
   * repeatedly from the file until the requested number of bytes are
   * read. This method blocks until the requested number of bytes are
   * read, the end of the stream is detected, or an exception is thrown.
   *
   * @param b the buffer into which the data is read.
   * @param off the start offset of the data.
   * @param len the number of bytes to read.
   * @throws EOFException if this file reaches the end before reading all the bytes.
   * @throws IOException if an I/O error occurs.
   */
  public final void readFully(byte b[], int off, int len) throws IOException {
    int n = 0;
    do {
      int count = this.read(b, off + n, len - n);
      if (count < 0) {
        throw new EOFException();
      }
      n += count;
    } while (n < len);
  }

  /**
   * Attempts to skip over {@code n} bytes of input discarding the
   * skipped bytes.
   * <p>
   *
   * This method may skip over some smaller number of bytes, possibly zero.
   * This may result from any of a number of conditions; reaching end of
   * file before {@code n} bytes have been skipped is only one
   * possibility. This method never throws an {@code EOFException}.
   * The actual number of bytes skipped is returned.  If {@code n}
   * is negative, no bytes are skipped.
   *
   * @param n the number of bytes to be skipped.
   * @return the actual number of bytes skipped.
   * @throws IOException if an I/O error occurs.
   */
  public int skipBytes(int n) throws IOException {
    long pos;
    long len;
    long newpos;

    if (n <= 0) {
      return 0;
    }
    pos = getFilePointer();
    len = length();
    newpos = pos + n;
    if (newpos > len) {
      newpos = len;
    }
    seek(newpos);

        /* return the actual number of bytes skipped */
    return (int) (newpos - pos);
  }

  // 'Write' primitives

  /**
   * Writes the specified byte to this file. The write starts at
   * the current file pointer.
   *
   * @param b the {@code byte} to be written.
   * @throws IOException if an I/O error occurs.
   */
  public void write(int b) throws IOException {
    write0(b);
  }

  private native void write0(int b) throws IOException;

  /**
   * Writes a sub array as a sequence of bytes.
   *
   * @param b the data to be written
   * @param off the start offset in the data
   * @param len the number of bytes that are written
   * @throws IOException If an I/O error has occurred.
   */
  private native void writeBytes(byte b[], int off, int len) throws IOException;

  /**
   * Writes {@code b.length} bytes from the specified byte array
   * to this file, starting at the current file pointer.
   *
   * @param b the data.
   * @throws IOException if an I/O error occurs.
   */
  public void write(byte b[]) throws IOException {
    writeBytes(b, 0, b.length);
  }

  /**
   * Writes {@code len} bytes from the specified byte array
   * starting at offset {@code off} to this file.
   *
   * @param b the data.
   * @param off the start offset in the data.
   * @param len the number of bytes to write.
   * @throws IOException if an I/O error occurs.
   */
  public void write(byte b[], int off, int len) throws IOException {
    writeBytes(b, off, len);
  }

  // 'Random access' stuff

  /**
   * Returns the current offset in this file.
   *
   * @return the offset from the beginning of the file, in bytes, at which the next read or write
   * occurs.
   * @throws IOException if an I/O error occurs.
   */
  public native long getFilePointer() throws IOException;

  /**
   * Sets the file-pointer offset, measured from the beginning of this
   * file, at which the next read or write occurs.  The offset may be
   * set beyond the end of the file. Setting the offset beyond the end
   * of the file does not change the file length.  The file length will
   * change only by writing after the offset has been set beyond the end
   * of the file.
   *
   * @param pos the offset position, measured in bytes from the beginning of the file, at which to
   * set the file pointer.
   * @throws IOException if {@code pos} is less than {@code 0} or if an I/O error occurs.
   */
  public void seek(long pos) throws IOException {
    if (pos < 0) {
      throw new IOException("Negative seek offset");
    } else {
      seek0(pos);
    }
  }

  private native void seek0(long pos) throws IOException;

  /**
   * Returns the length of this file.
   *
   * @return the length of this file, measured in bytes.
   * @throws IOException if an I/O error occurs.
   */
  public native long length() throws IOException;

  /**
   * Sets the length of this file.
   *
   * <p> If the present length of the file as returned by the
   * {@code length} method is greater than the {@code newLength}
   * argument then the file will be truncated.  In this case, if the file
   * offset as returned by the {@code getFilePointer} method is greater
   * than {@code newLength} then after this method returns the offset
   * will be equal to {@code newLength}.
   *
   * <p> If the present length of the file as returned by the
   * {@code length} method is smaller than the {@code newLength}
   * argument then the file will be extended.  In this case, the contents of
   * the extended portion of the file are not defined.
   *
   * @param newLength The desired length of the file
   * @throws IOException If an I/O error occurs
   * @since 1.2
   */
  public native void setLength(long newLength) throws IOException;

  /**
   * Closes this random access file stream and releases any system
   * resources associated with the stream. A closed random access
   * file cannot perform input or output operations and cannot be
   * reopened.
   *
   * <p> If this file has an associated channel then the channel is closed
   * as well.
   *
   * @throws IOException if an I/O error occurs.
   * @revised 1.4
   * @spec JSR-51
   */
  public void close() throws IOException {
    synchronized (closeLock) {
      if (closed) {
        return;
      }
      closed = true;
    }
    if (channel != null) {
      channel.close();
    }

    fd.closeAll(new Closeable() {
      public void close() throws IOException {
        close0();
      }
    });
  }

  //
  //  Some "reading/writing Java data types" methods stolen from
  //  DataInputStream and DataOutputStream.
  //

  /**
   * Reads a {@code boolean} from this file. This method reads a
   * single byte from the file, starting at the current file pointer.
   * A value of {@code 0} represents
   * {@code false}. Any other value represents {@code true}.
   * This method blocks until the byte is read, the end of the stream
   * is detected, or an exception is thrown.
   *
   * @return the {@code boolean} value read.
   * @throws EOFException if this file has reached the end.
   * @throws IOException if an I/O error occurs.
   */
  public final boolean readBoolean() throws IOException {
    int ch = this.read();
    if (ch < 0) {
      throw new EOFException();
    }
    return (ch != 0);
  }

  /**
   * Reads a signed eight-bit value from this file. This method reads a
   * byte from the file, starting from the current file pointer.
   * If the byte read is {@code b}, where
   * <code>0&nbsp;&lt;=&nbsp;b&nbsp;&lt;=&nbsp;255</code>,
   * then the result is:
   * <blockquote><pre>
   *     (byte)(b)
   * </pre></blockquote>
   * <p>
   * This method blocks until the byte is read, the end of the stream
   * is detected, or an exception is thrown.
   *
   * @return the next byte of this file as a signed eight-bit {@code byte}.
   * @throws EOFException if this file has reached the end.
   * @throws IOException if an I/O error occurs.
   */
  public final byte readByte() throws IOException {
    int ch = this.read();
    if (ch < 0) {
      throw new EOFException();
    }
    return (byte) (ch);
  }

  /**
   * Reads an unsigned eight-bit number from this file. This method reads
   * a byte from this file, starting at the current file pointer,
   * and returns that byte.
   * <p>
   * This method blocks until the byte is read, the end of the stream
   * is detected, or an exception is thrown.
   *
   * @return the next byte of this file, interpreted as an unsigned eight-bit number.
   * @throws EOFException if this file has reached the end.
   * @throws IOException if an I/O error occurs.
   */
  public final int readUnsignedByte() throws IOException {
    int ch = this.read();
    if (ch < 0) {
      throw new EOFException();
    }
    return ch;
  }

  /**
   * Reads a signed 16-bit number from this file. The method reads two
   * bytes from this file, starting at the current file pointer.
   * If the two bytes read, in order, are
   * {@code b1} and {@code b2}, where each of the two values is
   * between {@code 0} and {@code 255}, inclusive, then the
   * result is equal to:
   * <blockquote><pre>
   *     (short)((b1 &lt;&lt; 8) | b2)
   * </pre></blockquote>
   * <p>
   * This method blocks until the two bytes are read, the end of the
   * stream is detected, or an exception is thrown.
   *
   * @return the next two bytes of this file, interpreted as a signed 16-bit number.
   * @throws EOFException if this file reaches the end before reading two bytes.
   * @throws IOException if an I/O error occurs.
   */
  public final short readShort() throws IOException {
    int ch1 = this.read();
    int ch2 = this.read();
    if ((ch1 | ch2) < 0) {
      throw new EOFException();
    }
    return (short) ((ch1 << 8) + (ch2 << 0));
  }

  /**
   * Reads an unsigned 16-bit number from this file. This method reads
   * two bytes from the file, starting at the current file pointer.
   * If the bytes read, in order, are
   * {@code b1} and {@code b2}, where
   * <code>0&nbsp;&lt;=&nbsp;b1, b2&nbsp;&lt;=&nbsp;255</code>,
   * then the result is equal to:
   * <blockquote><pre>
   *     (b1 &lt;&lt; 8) | b2
   * </pre></blockquote>
   * <p>
   * This method blocks until the two bytes are read, the end of the
   * stream is detected, or an exception is thrown.
   *
   * @return the next two bytes of this file, interpreted as an unsigned 16-bit integer.
   * @throws EOFException if this file reaches the end before reading two bytes.
   * @throws IOException if an I/O error occurs.
   */
  public final int readUnsignedShort() throws IOException {
    int ch1 = this.read();
    int ch2 = this.read();
    if ((ch1 | ch2) < 0) {
      throw new EOFException();
    }
    return (ch1 << 8) + (ch2 << 0);
  }

  /**
   * Reads a character from this file. This method reads two
   * bytes from the file, starting at the current file pointer.
   * If the bytes read, in order, are
   * {@code b1} and {@code b2}, where
   * <code>0&nbsp;&lt;=&nbsp;b1,&nbsp;b2&nbsp;&lt;=&nbsp;255</code>,
   * then the result is equal to:
   * <blockquote><pre>
   *     (char)((b1 &lt;&lt; 8) | b2)
   * </pre></blockquote>
   * <p>
   * This method blocks until the two bytes are read, the end of the
   * stream is detected, or an exception is thrown.
   *
   * @return the next two bytes of this file, interpreted as a {@code char}.
   * @throws EOFException if this file reaches the end before reading two bytes.
   * @throws IOException if an I/O error occurs.
   */
  public final char readChar() throws IOException {
    int ch1 = this.read();
    int ch2 = this.read();
    if ((ch1 | ch2) < 0) {
      throw new EOFException();
    }
    return (char) ((ch1 << 8) + (ch2 << 0));
  }

  /**
   * Reads a signed 32-bit integer from this file. This method reads 4
   * bytes from the file, starting at the current file pointer.
   * If the bytes read, in order, are {@code b1},
   * {@code b2}, {@code b3}, and {@code b4}, where
   * <code>0&nbsp;&lt;=&nbsp;b1, b2, b3, b4&nbsp;&lt;=&nbsp;255</code>,
   * then the result is equal to:
   * <blockquote><pre>
   *     (b1 &lt;&lt; 24) | (b2 &lt;&lt; 16) + (b3 &lt;&lt; 8) + b4
   * </pre></blockquote>
   * <p>
   * This method blocks until the four bytes are read, the end of the
   * stream is detected, or an exception is thrown.
   *
   * @return the next four bytes of this file, interpreted as an {@code int}.
   * @throws EOFException if this file reaches the end before reading four bytes.
   * @throws IOException if an I/O error occurs.
   */
  public final int readInt() throws IOException {
    int ch1 = this.read();
    int ch2 = this.read();
    int ch3 = this.read();
    int ch4 = this.read();
    if ((ch1 | ch2 | ch3 | ch4) < 0) {
      throw new EOFException();
    }
    return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
  }

  /**
   * Reads a signed 64-bit integer from this file. This method reads eight
   * bytes from the file, starting at the current file pointer.
   * If the bytes read, in order, are
   * {@code b1}, {@code b2}, {@code b3},
   * {@code b4}, {@code b5}, {@code b6},
   * {@code b7}, and {@code b8,} where:
   * <blockquote><pre>
   *     0 &lt;= b1, b2, b3, b4, b5, b6, b7, b8 &lt;=255,
   * </pre></blockquote>
   * <p>
   * then the result is equal to:
   * <blockquote><pre>
   *     ((long)b1 &lt;&lt; 56) + ((long)b2 &lt;&lt; 48)
   *     + ((long)b3 &lt;&lt; 40) + ((long)b4 &lt;&lt; 32)
   *     + ((long)b5 &lt;&lt; 24) + ((long)b6 &lt;&lt; 16)
   *     + ((long)b7 &lt;&lt; 8) + b8
   * </pre></blockquote>
   * <p>
   * This method blocks until the eight bytes are read, the end of the
   * stream is detected, or an exception is thrown.
   *
   * @return the next eight bytes of this file, interpreted as a {@code long}.
   * @throws EOFException if this file reaches the end before reading eight bytes.
   * @throws IOException if an I/O error occurs.
   */
  public final long readLong() throws IOException {
    return ((long) (readInt()) << 32) + (readInt() & 0xFFFFFFFFL);
  }

  /**
   * Reads a {@code float} from this file. This method reads an
   * {@code int} value, starting at the current file pointer,
   * as if by the {@code readInt} method
   * and then converts that {@code int} to a {@code float}
   * using the {@code intBitsToFloat} method in class
   * {@code Float}.
   * <p>
   * This method blocks until the four bytes are read, the end of the
   * stream is detected, or an exception is thrown.
   *
   * @return the next four bytes of this file, interpreted as a {@code float}.
   * @throws EOFException if this file reaches the end before reading four bytes.
   * @throws IOException if an I/O error occurs.
   * @see java.io.RandomAccessFile#readInt()
   * @see java.lang.Float#intBitsToFloat(int)
   */
  public final float readFloat() throws IOException {
    return Float.intBitsToFloat(readInt());
  }

  /**
   * Reads a {@code double} from this file. This method reads a
   * {@code long} value, starting at the current file pointer,
   * as if by the {@code readLong} method
   * and then converts that {@code long} to a {@code double}
   * using the {@code longBitsToDouble} method in
   * class {@code Double}.
   * <p>
   * This method blocks until the eight bytes are read, the end of the
   * stream is detected, or an exception is thrown.
   *
   * @return the next eight bytes of this file, interpreted as a {@code double}.
   * @throws EOFException if this file reaches the end before reading eight bytes.
   * @throws IOException if an I/O error occurs.
   * @see java.io.RandomAccessFile#readLong()
   * @see java.lang.Double#longBitsToDouble(long)
   */
  public final double readDouble() throws IOException {
    return Double.longBitsToDouble(readLong());
  }

  /**
   * Reads the next line of text from this file.  This method successively
   * reads bytes from the file, starting at the current file pointer,
   * until it reaches a line terminator or the end
   * of the file.  Each byte is converted into a character by taking the
   * byte's value for the lower eight bits of the character and setting the
   * high eight bits of the character to zero.  This method does not,
   * therefore, support the full Unicode character set.
   *
   * <p> A line of text is terminated by a carriage-return character
   * ({@code '\u005Cr'}), a newline character ({@code '\u005Cn'}), a
   * carriage-return character immediately followed by a newline character,
   * or the end of the file.  Line-terminating characters are discarded and
   * are not included as part of the string returned.
   *
   * <p> This method blocks until a newline character is read, a carriage
   * return and the byte following it are read (to see if it is a newline),
   * the end of the file is reached, or an exception is thrown.
   *
   * @return the next line of text from this file, or null if end of file is encountered before even
   * one byte is read.
   * @throws IOException if an I/O error occurs.
   */

  public final String readLine() throws IOException {
    StringBuffer input = new StringBuffer();
    int c = -1;
    boolean eol = false;

    while (!eol) {
      switch (c = read()) {
        case -1:
        case '\n':
          eol = true;
          break;
        case '\r':
          eol = true;
          long cur = getFilePointer();
          if ((read()) != '\n') {
            seek(cur);
          }
          break;
        default:
          input.append((char) c);
          break;
      }
    }

    if ((c == -1) && (input.length() == 0)) {
      return null;
    }
    return input.toString();
  }

  /**
   * Reads in a string from this file. The string has been encoded
   * using a
   * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
   * format.
   * <p>
   * The first two bytes are read, starting from the current file
   * pointer, as if by
   * {@code readUnsignedShort}. This value gives the number of
   * following bytes that are in the encoded string, not
   * the length of the resulting string. The following bytes are then
   * interpreted as bytes encoding characters in the modified UTF-8 format
   * and are converted into characters.
   * <p>
   * This method blocks until all the bytes are read, the end of the
   * stream is detected, or an exception is thrown.
   *
   * @return a Unicode string.
   * @throws EOFException if this file reaches the end before reading all the bytes.
   * @throws IOException if an I/O error occurs.
   * @throws UTFDataFormatException if the bytes do not represent valid modified UTF-8 encoding of a
   * Unicode string.
   * @see java.io.RandomAccessFile#readUnsignedShort()
   */
  public final String readUTF() throws IOException {
    return DataInputStream.readUTF(this);
  }

  /**
   * Writes a {@code boolean} to the file as a one-byte value. The
   * value {@code true} is written out as the value
   * {@code (byte)1}; the value {@code false} is written out
   * as the value {@code (byte)0}. The write starts at
   * the current position of the file pointer.
   *
   * @param v a {@code boolean} value to be written.
   * @throws IOException if an I/O error occurs.
   */
  public final void writeBoolean(boolean v) throws IOException {
    write(v ? 1 : 0);
    //written++;
  }

  /**
   * Writes a {@code byte} to the file as a one-byte value. The
   * write starts at the current position of the file pointer.
   *
   * @param v a {@code byte} value to be written.
   * @throws IOException if an I/O error occurs.
   */
  public final void writeByte(int v) throws IOException {
    write(v);
    //written++;
  }

  /**
   * Writes a {@code short} to the file as two bytes, high byte first.
   * The write starts at the current position of the file pointer.
   *
   * @param v a {@code short} to be written.
   * @throws IOException if an I/O error occurs.
   */
  public final void writeShort(int v) throws IOException {
    write((v >>> 8) & 0xFF);
    write((v >>> 0) & 0xFF);
    //written += 2;
  }

  /**
   * Writes a {@code char} to the file as a two-byte value, high
   * byte first. The write starts at the current position of the
   * file pointer.
   *
   * @param v a {@code char} value to be written.
   * @throws IOException if an I/O error occurs.
   */
  public final void writeChar(int v) throws IOException {
    write((v >>> 8) & 0xFF);
    write((v >>> 0) & 0xFF);
    //written += 2;
  }

  /**
   * Writes an {@code int} to the file as four bytes, high byte first.
   * The write starts at the current position of the file pointer.
   *
   * @param v an {@code int} to be written.
   * @throws IOException if an I/O error occurs.
   */
  public final void writeInt(int v) throws IOException {
    write((v >>> 24) & 0xFF);
    write((v >>> 16) & 0xFF);
    write((v >>> 8) & 0xFF);
    write((v >>> 0) & 0xFF);
    //written += 4;
  }

  /**
   * Writes a {@code long} to the file as eight bytes, high byte first.
   * The write starts at the current position of the file pointer.
   *
   * @param v a {@code long} to be written.
   * @throws IOException if an I/O error occurs.
   */
  public final void writeLong(long v) throws IOException {
    write((int) (v >>> 56) & 0xFF);
    write((int) (v >>> 48) & 0xFF);
    write((int) (v >>> 40) & 0xFF);
    write((int) (v >>> 32) & 0xFF);
    write((int) (v >>> 24) & 0xFF);
    write((int) (v >>> 16) & 0xFF);
    write((int) (v >>> 8) & 0xFF);
    write((int) (v >>> 0) & 0xFF);
    //written += 8;
  }

  /**
   * Converts the float argument to an {@code int} using the
   * {@code floatToIntBits} method in class {@code Float},
   * and then writes that {@code int} value to the file as a
   * four-byte quantity, high byte first. The write starts at the
   * current position of the file pointer.
   *
   * @param v a {@code float} value to be written.
   * @throws IOException if an I/O error occurs.
   * @see java.lang.Float#floatToIntBits(float)
   */
  public final void writeFloat(float v) throws IOException {
    writeInt(Float.floatToIntBits(v));
  }

  /**
   * Converts the double argument to a {@code long} using the
   * {@code doubleToLongBits} method in class {@code Double},
   * and then writes that {@code long} value to the file as an
   * eight-byte quantity, high byte first. The write starts at the current
   * position of the file pointer.
   *
   * @param v a {@code double} value to be written.
   * @throws IOException if an I/O error occurs.
   * @see java.lang.Double#doubleToLongBits(double)
   */
  public final void writeDouble(double v) throws IOException {
    writeLong(Double.doubleToLongBits(v));
  }

  /**
   * Writes the string to the file as a sequence of bytes. Each
   * character in the string is written out, in sequence, by discarding
   * its high eight bits. The write starts at the current position of
   * the file pointer.
   *
   * @param s a string of bytes to be written.
   * @throws IOException if an I/O error occurs.
   */
  @SuppressWarnings("deprecation")
  public final void writeBytes(String s) throws IOException {
    int len = s.length();
    byte[] b = new byte[len];
    s.getBytes(0, len, b, 0);
    writeBytes(b, 0, len);
  }

  /**
   * Writes a string to the file as a sequence of characters. Each
   * character is written to the data output stream as if by the
   * {@code writeChar} method. The write starts at the current
   * position of the file pointer.
   *
   * @param s a {@code String} value to be written.
   * @throws IOException if an I/O error occurs.
   * @see java.io.RandomAccessFile#writeChar(int)
   */
  public final void writeChars(String s) throws IOException {
    int clen = s.length();
    int blen = 2 * clen;
    byte[] b = new byte[blen];
    char[] c = new char[clen];
    s.getChars(0, clen, c, 0);
    for (int i = 0, j = 0; i < clen; i++) {
      b[j++] = (byte) (c[i] >>> 8);
      b[j++] = (byte) (c[i] >>> 0);
    }
    writeBytes(b, 0, blen);
  }

  /**
   * Writes a string to the file using
   * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
   * encoding in a machine-independent manner.
   * <p>
   * First, two bytes are written to the file, starting at the
   * current file pointer, as if by the
   * {@code writeShort} method giving the number of bytes to
   * follow. This value is the number of bytes actually written out,
   * not the length of the string. Following the length, each character
   * of the string is output, in sequence, using the modified UTF-8 encoding
   * for each character.
   *
   * @param str a string to be written.
   * @throws IOException if an I/O error occurs.
   */
  public final void writeUTF(String str) throws IOException {
    DataOutputStream.writeUTF(str, this);
  }

  private static native void initIDs();

  private native void close0() throws IOException;

  static {
    initIDs();
  }
}
